No difference between organic and conventional arable farms in the numbers of bumblebees, butterflies and day-flying moths on field boundaries in Finland
Published Source
Ekroos J., Piha M. & Tiainen J. (2008) Role of organic and conventional field boundaries on boreal bumblebees and butterflies.
Agriculture, Ecosystems and Environment, 124, 155-159 (added by: Dicks L. 2010).
Background
Organic farmers receive subsidies through European agri-environment schemes. This study compares bumblebees, butterflies and day-flying moths on organic and conventional field boundaries in Finland.
Action
Three 100 ha study sites were used, 1-2 km apart with 5-40% organically farmed arable fields and 5-8% woodland. Organic farmers use no synthetic fertilizers or pesticides. Organic farms in this study had been certified as organic since 1996 or 1997.
At each site, ten 50 m transects were established along field boundaries in the quadrant with the most and in the quadrant with the least woodland cover (20 transects at each site). Overall, 15 transects were on organic farms and 45 on conventional farms. Five transects were omitted from the analysis because they were on moist meadow on conventional farms, a habitat type with no equivalent on organic farm transects.
Day-flying moths, butterflies and bumblebees were recorded on transect walks, on days with temperatures of at least 17° C if sunny, at least 22° C if overcast, every two weeks from late May to late August 2001-2003. In July each year, the percentage cover of flowering plants on each transect was estimated.
Consequences
There were no statistically significant differences between organic and conventional farms in the numbers or species richness of butterflies and moths or bumblebees.
On average, 9.4 butterflies from one species were recorded per transect on conventional farm field boundaries, and 9.0 butterflies from one species on organic farm field boundaries. For all day-flying Lepidoptera, 12.8 butterflies and day-flying moths were recorded per transect on conventional farm field boundaries, and 11.6 on organic farm field boundaries.
On average, three bumblebees from 1.1 species were recorded per transect on conventional farm field boundaries, and 3.8 bumblebees from 1.4 species on organic farm field boundaries.
In total, between 34 and 52 species of butterfly and day-flying moth were recorded each year, and between 12 and 14 bumblebee species. The abundances of butterflies, moths and bumblebees, and the number of butterfly species were correlated with the quantity (percentage cover) of nectar flowers available.